The present invention relates to a method of evaluating a film thickness, a method of detecting a polishing terminal, and a device-manufacturing apparatus. More particularly, the present invention relates to a method of evaluating a film thickness and a method of detecting a polishing terminal when an insulating film formed on a device is polished with a chemical mechanical polishing method. The present invention also relates to an apparatus for manufacturing a device while evaluating a film thickness.
In a process of manufacturing a semiconductor device, a chemical mechanical polishing (CMP) method has been widely used for polishing an insulating film and a metallic film formed on a wafer. In the CMP method, it is necessary to accurately evaluate an actual thickness of an insulating film or a metallic film during a polishing process and determine a point of terminating the polishing process (polishing terminal).
As a conventional method of detecting the polishing terminal of a light-permeable thin film such as an oxidized film or nitride film, for example, a method has been proposed in which a beam is irradiated onto a polished surface of a wafer, and a spectra intensity distribution of a reflective beam is measured to determine the polishing terminal (refer to Patent document 1). In the method, light from a light source is split into parallel beams via a lens and irradiated onto a polished surface of a wafer. A beam-shielding slit selects zero dimension (i.e., a regular reflection beam) beams reflected from the polished surface of the wafer, and the spectra intensity distribution is measured. The spectra intensity distribution is compared with spectra characteristics stored in advance to detect the polishing terminal.
As another method of detecting the polishing terminal of a light-permeable thin film, a method has been proposed in which a color component of a reflective beam is detected to determine the polishing terminal of a light-permeable thin film (refer to Patent document 2). In the method, light from a light source is guided via a light guide member and irradiated onto a polished surface of a wafer. The light guide guides light reflected from the polished surface to a color sensor for detecting a color component. The color component is compared with a reference color component stored in advance to determine the polishing terminal.
Patent Document 1: Japanese Patent Publication (Kokai) No. 2000-186918 (paragraphs 0034-0036, and FIGS. 3-5)
Patent Document 2: Japanese Patent Publication (Kokai) No. 2000-183001 (paragraphs 0033-0036, and FIGS. 1 and 9)
In the method of detecting the polishing terminal based on the spectra intensity distribution of light reflected from the polished surface of a wafer, it is necessary to precisely irradiate parallel beams onto a polished surface, and it is difficult to perform an optical adjustment. Further, in the method, when a polished surface is slightly inclined or an optical system has a slight aberration, regular reflection beams may generate an image outside a narrow beam-shielding slit. Accordingly, regular reflection beams passing through the beam-shielding slit are decreased, and an intensity of beams for detecting the polishing terminal is attenuated, thereby lowering detection sensitivity. Further, it is necessary to provide an irradiating and receiving optical system using a beam splitter for separating irradiating beams from reflected beams, thereby lowering beam efficiency.
In the method of detecting the polishing terminal by comparing a color component of light reflected from a polished surface of a wafer, the color sensor detects the color component of reflective beams without splitting. Accordingly, it is difficult to precisely analyze colors of RGB and accurately detect the polishing terminal.
In view of the above problems, the present invention has been developed, and an object of the present invention is to provide a method of evaluating a film thickness in which it is possible to accurately evaluate an actual thickness of a film during a polishing process.
Another object of the present invention is to provide a method of detecting the polishing terminal in which it is possible to accurately evaluate an actual thickness of a film during a polishing process and detect the polishing terminal.
A further object of the present invention is to provide a device-manufacturing apparatus capable of manufacturing a device while accurately evaluating a thickness of a film during a polishing process.
Further objects and advantages of the present invention will be apparent from the following description of the invention.